MVC使用帮助程序命名空间中的方法

Question

I have the following in ~/Helpers/Helpers.cs:

namespace AdjusterSave.Helpers
{
    public class Helpers : Controller
    {
        // various methods such as the following...

        public void GetDropdowns()
        {
        }
    }
}

I am trying to use these in my ~/Controllers/AdjusterController.cs file by including it like so:

using AdjusterSave.Helpers;

However, I continue to get the following error when trying to use the methods. When I call this:

GetDropdowns();

I get this error:

The name 'GetDropdowns' does not exist in the current context.

Edit:

Trying to use method like so (in ~/Controllers/AdjusterController.cs):

public ActionResult ViewProfile()
{
    // a bunch of code like this:
    User user = db.Users.Where(x => x.username == HttpContext.User.Identity.Name).FirstOrDefault();

    AdjusterViewProfileInfo model = new AdjusterViewProfileInfo();

    // get name
    model.namePrefix = user.namePrefix;
    model.firstName = user.firstName;
    model.middleInitial = user.middleInitial;
    model.lastName = user.lastName;
    model.nameSuffix = user.nameSuffix;

    // end then, finally,

    GetDropdowns();

    // followed by...

    TempData["CurrentPage"] = "ViewProfile";

    return View("", _layout, model);
}

Edit:

GetDropdowns Example:

public void GetDropdowns(this Controller controller)
{
    // get name prefixes
    List<SelectListItem> prefixList = new List<SelectListItem>();

    prefixList.Add(new SelectListItem { Value = "Mr.", Text = "Mr." });
    prefixList.Add(new SelectListItem { Value = "Mrs.", Text = "Mrs." });
    prefixList.Add(new SelectListItem { Value = "Ms.", Text = "Ms." });

    ViewBag.PrefixList = new SelectList(prefixList, "Value", "Text");

}

Answer 1

You are doing it wrong. What you need to do is to create a static class like this:

public static class Helpers
{
    public static void GetDropdowns(this Controller controller)
    {
        // var username = controller.HttpContext.User.Identity.Name;

        // get name prefixes
        List<SelectListItem> prefixList = new List<SelectListItem>();

        prefixList.Add(new SelectListItem { Value = "Mr.", Text = "Mr." });
        prefixList.Add(new SelectListItem { Value = "Mrs.", Text = "Mrs." });
        prefixList.Add(new SelectListItem { Value = "Ms.", Text = "Ms." });

        controller.ViewBag.PrefixList = new SelectList(prefixList, "Value", "Text");

     }     
}

And, you can use it in your Controller like this:

this.GetDropdowns();

Answer 2

You can use the Extension Methods instead inheriths from Controller:

public static class Helpers
{
    public static void GetDropdowns(this Controller controller)
    {
        // do something with the "controller", for sample:
        controller.ViewBag = new List<string>();
    }
}

Everything you need to access on the controller you can do by the controller parameter.

And in your controller you can do something like this:

public ActionResult Index()
{
    // just call it, and the .net framework will pass "this" controller to your extension methodo
    GetDropdowns();
}

Answer 3

If you want to call GetDropdowns() you can:

Instantiate Helpers and call it:

new Helpers().GetDropdowns();

Make method GetDropdowns static:

public static void GetDropdowns()
{
}

and then call it:

Helpers.GetDropdowns();

You may also inherit AdjusterController from Helpers:

public class AdjusterController : Helpers
{
}

and then call it just as you did. Everything depends on what you're interested in. I guess you should not inherit Helpers from Controller and make the method static, but it's just a guess.